Organic EL elements have been actively researched and developed. In the fundamental structure of an organic EL element, a layer containing a light-emitting organic compound is interposed between a pair of electrodes. By applying voltage to this element, light emission from the light-emitting organic compound can be obtained.
The organic EL element can be formed into a film shape; thus, a large-area element can easily be formed. Therefore, the organic EL element has a high utility value as a surface light source that can be applied to lighting or the like.
For example, a lighting device using an organic EL element is disclosed in Patent Document 1.
In addition, as for an organic EL element, there are a top-emission type in which light is extracted from the side of a substrate, on which an organic EL element is formed; a bottom-emission type in which light is extracted from the side of the substrate, which is opposite to the side on which the organic EL element is formed; and a dual-emission type in which light is extracted from both the sides.